The first step towards a Finite Volume discretization (for a deeper insight see [1]}) of the problem is the division of the domain \(\Omega (\pi )\)  into a tessellation \(\mathcal {T}(\pi )\)  composed by a certain number \(N_h\)  of cells \(\Omega _i(\pi )\) , so that:
\(\mathcal {T}(\pi ) = \lbrace  \Omega _i(\pi ) \rbrace _{i=1}^{N_h}, \hspace{28.45274pt} \bigcup _{i=1}^{N_h} \Omega _i (\pi ) = \Omega (\pi ),\) 
